Endocrine Abstracts

Hyperprolactinemia is a condition that can present itself in many different contexts ranging from physiological during pregnancy, pharmacological (e.g., due to antidepressants or antipsychotics) or truly pathological. Pathological mechanisms of hyperprolactinemia include pituitary tumors, tumor metastases, autoimmune diseases and ectopic prolactin producing tumors. In addition, prolactin values may be elevated due to macroprolactin. Detection of macroprolactin through PEG-precipitation is performed under various conditions in different laboratories and reporting of post PEG-prolactin is performed through different approaches. Also, prolactin assays have distinct sensitivity towards macroprolactin. We show the impact of switch from one prolactin measuring method (Siemens Immulite XPi) to another (Roche Cobas Pro®). Should gender specific prolactin monomeric reference values be used, on average approximately 25% of all hyperprolactinemic samples are deemed hyperprolactinemic measured by both methods (Table 1). When adding <50% recovery (Percent recovery=(post-PEG prolactin ÷ pre-PEG prolactin) × 100; <50% Recovery means that more than 50% of the measured pre-PEG prolactin comprises of prolactin adducts (e.g., macroprolactin).) to the abovementioned rule of leveling within the monomeric reference intervals, a substantially smaller percentage of Siemens and Roche samples would be assumed to be macroprolactinemic with 10.8% and 2.3% respectively. This would especially be impactful if no post-PEG prolactin value would be reported along with the%-recovery and exemplifies the importance of being acquainted with the rules a laboratory sets for the presence of macroprolactin, but also the assay the lab utilizes. Unfortunately, such technicalities can impossibly be captured in guidelines and might be unknown to the clinician even though they could potentially impact decision making (especially when the post-PEG prolactin value is not reported and laboratory reports only recovery value). Thus, in final reporting, it is very important to define laboratory specific monomeric reference intervals when the presence of macroprolactin is defined by normalizing within monomeric reference intervals. In addition, post-PEG prolactin values should be reported when utilizing recovery as a defining factor for the presence of macroprolactin in order to prevent misdiagnosis. Differences between both reporting strategies might be smaller or larger depending on the assay used and its sensitivity to macroprolactin. Therefore, the likelihood of the presence of true pathological hyperprolactinemia always needs to be assessed in the context of the assay used, the sensitivity of the assay to prolactin adducts, type of PEG polymer used and the manner in which prolactin adducts are reported by the laboratory.